从Centos 7服务器发送邮件不起作用

Question

In my java application I have a module that allows to send mails

application.yml:

...
    mail:
        host: smtp.gmail.com
        port: 587
        username: xxxxxx@gmail.com  #Replace this field with your Gmail username.
        password: xxxxxxx           #Replace this field with your Gmail password.
        protocol: smtp
        tls: true
        properties.mail.smtp:
            auth: true
            starttls.enable: true
            ssl.trust: smtp.gmail.com
...

MailService.java:

...
    @Async
    public void sendEmail(String to, String subject, String content, boolean isMultipart, boolean isHtml) {
        log.debug("Send email[multipart '{}' and html '{}'] to '{}' with subject '{}' and content={}",
            isMultipart, isHtml, to, subject, content);

        // Prepare message using a Spring helper
        MimeMessage mimeMessage = javaMailSender.createMimeMessage();
        try {
            MimeMessageHelper message = new MimeMessageHelper(mimeMessage, isMultipart, StandardCharsets.UTF_8.name());
            message.setTo(to);
            message.setFrom(Properties.getMail().getFrom());
            message.setSubject(subject);
            message.setText(content, isHtml);
            javaMailSender.send(mimeMessage);
            log.debug("Sent email to User '{}'", to);
        } catch (Exception e) {
            if (log.isDebugEnabled()) {
                log.warn("Email could not be sent to user '{}'", to, e);
            } else {
                log.warn("Email could not be sent to user '{}': {}", to, e.getMessage());
            }
        }
    }
...

When I use my application locally (Windows 10) I receive my emails. But when I deploy my application on my server Centos 7 I do not receive any mail and I have no error in my logs.

So I wonder if it is necessary to install a postfix or others on my server Centos 7 to relay the mail?

I opened port 587 25 on my Centos 7 firewall

Answer 1

So I wonder if it is necessary to install a postfix or others on my server Centos 7 to relay the mail?

It shouldn't be necessary. The Javamail API should be able to talk directly to an SMTP server without any local intermediary to relay the email.

I opened port 587 25 on my Centos 7 firewall

Unblocking out-bound connections on port 587 on your server's firewall would be necessary ... if it was blocked. But it is not usual to block outgoing ports.

It is more likely that outgoing connections on port 587 are blocked by your ISP or cloud provider. Check their policy on clients sending email.

Another possibility is that the emails are reaching the Google mail servers, but they get classified as spam ... and are silently filtered out.

---

You can get more clues as to what is actually happening by setting the mail.debug property to true , or by calling setDebug(true) on the mail Session object.